Large diameter atypical pigmented lesions (LDAPL)can be challenging to diagnose accurately usingpartial biopsies because of pathologic heterogeneity,while at the same time large excisions of these lesionsconfer significant morbidity to patients. Consequently,clinicians are often challenged by the managementof these lesions. In this case, we describe an elderlypatient with a history of multiple basal cell carcinomas,prior melanomas, and a family history of melanomawho presented with an irregularly pigmented brownand dark brown patch on his upper back. This lesionwas evaluated with multiple partial incisional biopsiesfrom the most atypical appearing areas of the lesionidentified on dermoscopy, each showing mild andmoderate atypical melanocytes. However, the patchcontinued to change clinically and eventually thepatient underwent a 5mm wide local excision, whichrevealed severely atypical melanocytic proliferationwith areas consistent with melanoma in situ. Thiscase highlights the need for clinicians to lower theirthreshold for excisional biopsy of LDAPL in high-riskpatients.